Ive read exhaustively on all of the common intake substitutes (Injen, BMW Perf, AFE) and I think this could potentially be better, all things considered.

On another note - I haven't been able to find a dyno or hard data on a solid intake + tune + exhaust setup. I have owned a E90 335i, E82 135i, and currently have an E92 M3. These are great cars but I primarily autocross and none of them are really competitive in their respective classes (D Stock, A Stock). I'm looking at building a 128i STX autocrosser and the jist of it would be:

I have no doubt the 3 stage intake could improve hp some but the part numbers for the exhaust manifolds of the X5 N52 is also different from the part numbers of my 128i N52. If you really wanted maximum hp, I think you would want the 3 stage, plus the X5 exhaust manifold (or aftermarket headers) and probably as much of the exhause sytem as you could afford or justify. Downpipes without catalyst would help too but not be legal, at least in the U. S..

It also seems like having the tuner there while the car was on the dyno is indicated by the results. Running back and forth to fine tune things seems like it would be frustrating.

Being that you're in NJ, your car might have the 3-stage manifold, too. All you need to find out is whether your car has the N52 or the N51. If it has the N51 (like my car), then it has the 3-stage manifold.

No offense, but why are you all so excited to have 3-stage intake manifolds? There's more to the high-output N52 than the intake manifold (not least of all the different ECU) and the N51 has a lower compression ratio besides. If anything, the N51 makes less power than the regular N52, but BMW publishes only one set of engine specs so as not to confuse consumers.

The only people that seem to get excited about the 3-stage manifold on the N51 are the people with the N52 that want the 3-stage manifold. My experience has been that most people think the 3-stage manifold only exists in the HO versions of the N52 and so they're surprised that the N51 has it also.

The N51 does have a slightly different power curve than the N52 with what feels like more mid-range and top-end power. Of course, it could just be that since you can feel the manifold changeover points (3,000 and 5,000 RPM, I think), it's placebo. If you do some research on the N51, you'll find that it's rumored that the N51 actually makes slightly more power than the N52. But since I don't have any proof, that's just a rumor.

since you can feel the manifold changeover points (3,000 and 5,000 RPM, I think), it's placebo.

That's really interesting to learn - I hated this about my e46 330i which I believe has a 2 stage manifold. It always felt like the car was really sluggish until it switched over, then it'd have a very faint 'hiccup' then pull strongly. The n52 with single stage is nice and smooth the whole way up.

Gents - I didnt want to start the N51/52 conversation - the intent here is to see who has found the best intake + ECU + exhaust setup to make the 128 a couple tenths faster. Based on all of the reading I have done, the 3 stage intake (NOT the one on the N51) is one of the core components that the high output N52s (e.g. 2006 330i E90 Sedan) uses to achieve 255 bhp vice 230 bhp.

JAF89f - Yes, the 128i stock is a pretty great setup, especially for autocross - thanks for posting a comment telling everyone posting comments about this is not worth the hassle.

Gents - I didnt want to start the N51/52 conversation - the intent here is to see who has found the best intake + ECU + exhaust setup to make the 128 a couple tenths faster. Based on all of the reading I have done, the 3 stage intake (NOT the one on the N51) is one of the core components that the high output N52s (e.g. 2006 330i E90 Sedan) uses to achieve 255 bhp vice 230 bhp.

JAF89f - Yes, the 128i stock is a pretty great setup, especially for autocross - thanks for posting a comment telling everyone posting comments about this is not worth the hassle.

This guy upgraded his 325i (an even more detuned N52) to ~260 hp and ~225 ft lbs (crank, correcting for drivetrain loss, compared to 230 hp and 200 ft lbs). He and has info on the manifold DIY (pretty much the same engine, so it should be similar..) and the 330i intake he used..

This guy upgraded his 325i (an even more detuned N52) to ~260 hp and ~225 ft lbs (crank, correcting for drivetrain loss, compared to 230 hp and 200 ft lbs). He and has info on the manifold DIY (pretty much the same engine, so it should be similar..) and the 330i intake he used..